CMSI 182 Intro to Computer Science. Week 13 Tuesday B.J. Johnson Doolan :25 10:40

Transcription

1 CMSI 182 Intro to Computer Science Week 13 Tuesday B.J. Johnson Doolan :25 10:40

2 Where We Are: History Lesson We re here! I/O Peripherals Internet Architecture RAM/ROM Applications O/S Programs Languages Router HD Database Algorithms Abstractions 2

3 This Week s Agenda Homework questions Networking Fundamentals Thanksgiving 3

4 Network Terms LAN: Local Area Network WAN: Wide Area Network CLAN/CWAN: Classified LAN/WAN AP: Access Point TCP: Transfer Control Protocol IP: Internet Protocol TCP/IP: you figure it out Open network: public domain Closed network: proprietary protocols 4

5 Network Types Bus Star Ring Token ring 5

6 Bus Network 6

7 Star Network 7

8 Token Ring Network 8

9 Network Parts Hub Basically just a miniature bus Plug in cables from computers They can all talk to each other All messages go to all computers MINIMAL networking Switch Smarter hub Can send messages only to specific computers Cuts down on unneeded network traffic 9

10 Network Parts Router Used to join multiple networks together Example is joining home network to the internet Fed from DSL modem, Cable modem, or FiOS Distributes signals to computers, printers, etc. Frequently have 4, 6, or more ports Have an input connection and fan-out outputs Frequently include wireless connectivity Used on LANs to join multiple sub-nets 10

11 Network Parts Repeater A smaller version of a hub Only has two ports; connects two buses All traffic is passed Bridge More complex repeater Two ports; connects two buses Only sends NEEDED traffic, like a switch 11

12 Network Parts Gateway Point at which a LAN connects to the internet Provides a passage between the LAN and the outside world of the internet May be simply a router May also be an entire infrastructure 12

13 Network Parts Ethernet Both hardware and protocol technologies IEEE 802 family IEEE basic standards descriptions IEEE wireless version B 11 Mbps, 2.4 GHz band G 54 Mbps, 2.4 GHz band N 54 Mbps, either 2.4 or 5 GHz Includes multiple input/multiple output antennas Channelized transmit bands Lots of other family members 13

14 Typical Home Network Internet connects to DSL modem Modem connects to router Router connects to home computers Wired (cabled) connections Wireless over b/g 14

15 Network Parts Security Can be set up in your router Router login from connected computer Usually address Usually factory login User name admin No password First thing to do is change those!! Router can be set to secure mode WAP and WEP WAP is more secure; requires a key Connection once with key is required 15

16 7 Deadly Network Layers Application file Xfer, , etc. Presentation protocol conversion, encryption/decryption, etc. Session process-to-process comm.; setup/ending sessions Transport msg. delivery btw. hosts Network address translation Data Link transfer of data using Physical transmit data over cable 16

17 The Internet Generic name Multiple networks All connected together Specific name THE Internet Started by DARPA and several academic institutions (UC Berkeley, UCLA, etc.) Linked world wide Multiple versions of LANs, WANs, corporate networks, etc. all connected together NOT invented by Al Gore! 17

18 Internet Composition Tiered architecture AOL Verizon ComCast Etc. You and me and our computers Copyright 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 18

19 Addressing for Access Each computer has a network interface card or NIC Each card has a specific Media Access Control (MAC) address A set of six hex values E.g., A Hard-wired onto the NIC This is how the computer is identified DSL connections are made using this May need to set up DSL with one main computer, then set the router settings to fool the DSL modem 19

20 Addressing for Access Each computer is assigned an IP address Static IP: assigned for the LAN and set forever in the computer settings Dynamic IP: assigned every time the computer connects to the LAN IP address is how the computer is identified for message traffic Consists of four octets xxx.xxx.xxx.xxx like Each octet is a byte; total is 32 bits 20

21 Domains, Names, Addresses People can t remember numbers, so we translate the octets to words First we get a top-level domain (TLD), like.com,.edu,.org,.gov; also country codes like.uk,.au, or.ru Then we get registered domains which must be approved by ICANN Usually assigned to ISPs like AOL, etc These two make up the domain like google.com or dmv.gov or lmu.edu ISPs can then allocated sub-domains which is where the left end comes from; like mail.google.com 21

22 Domain Name Lookup Names are stored in a Domain Name Server in the Domain Name System (DNS) When a browser points to an address the computer looks up the names on the DNS server for which it is configured You can find all this information for your computer from a terminal window Windows: ipconfig /all Mac: ifconfig 22

23 Internet Applications: Many types of protocols Three most common SMTP Simple Mail Transfer Protocol Oldest Primarily text transfer POP3 Post Office Protocol V.3 User downloads messages to her own host User manages message storage locally IMAP Internet Mail Access Protocol Messages stay on the mail server User can manage them on the server Allows server to manage infrastructure 23

24 Internet Applications: ftp FTP File Transfer Protocol Application program Client/server protocol Must be an ftp server program on remote User starts ftp client on local host File transfer in ascii/binary mode Also a number of GUI-based clients fireftp firefox plugin Filezilla ftp commander Many others, most are free 24

25 Internet Applications: telnet Not an acronym Provides a command line interface to the remote computer Start from terminal window by typing telnet <IP address> Often uses secure shell or SSH Putty free download secure program SSH itself can be used 25

26 Internet Applications: streams VoIP voice over internet protocol Radio pandora, grooveshark Video youtube, etc. Unicasting N-unicast one computer sends a stream to many other computers Multicast one computer sends messages to all computers on a sub-net 26

27 The World Wide Web Hypertext Hyperlinks HyperText Markup Language HyperText Transfer Protocol Web page Web site Browser / Web Server URL/URI 27

28 URL Parts Uniform Resource Locator (URL) Uniform Resource Identifier (URI) Uniform Resource Name (URN) For internet stuff, we only care about the URL Comprises: Protocol like Mnemonic name like The directory path to the file of interest The file name of the web page file Example: 28

29 For Thursday ~ HAPPY TURKEY DAY! Your assignment is to do whatever you need to do to get the most enjoyment of your holiday in whatever fashion you choose! 29

30 30